Ground electrode with a high heat transfer

ABSTRACT

A spark plug having a core or main body of insulating material, a central electrode extending through the core member, a second electrode forming a spark gap with the first electrode; and a member for mounting the second electrode in place and to provide a heat transfer path between the body and an adjacent engine block when the spark plug is operatively coupled thereto. The mounting member is preferably cup-shaped to permit it to be press fitted on one end of the body so that it can be carried thereby.

United States Patent Inventor Appl. No. Filed Patented GROUND ELECTRODE WITH A HIGH HEAT TRANSFER No references cited.

Primary Examiner-James W. Lawrence Assistant Examiner-C. R. Campbell Attorney-Townsend and Townsend ABSTRACT: A spark plug having a core or main body of insulating material, a central electrode extending through the core member, a second electrode forming a spark gap with the first 13 Claims 2 Drawing Figs electrode; and a member for mounting the second electrode in U.S.Cl. BIS/11.5, place and to provide a heat transfer path between the body 313/143 and an adjacent engine block when the spark plug is opera- Int.Cl. F23q 3/64, tively coupled thereto. The mounting member is preferably F23q 3/66; HOlt 13/20 cup-shaped to permit it to be press fitted on one end of the Field of Search 313/1 1.5, body so that it can be carried thereby.

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' X/ 7 I D ATTORNEYS GROUND ELECTRODE WITH A HIGH HEAT TRANSFER This invention relates to improvements in spark plugs of the type used in internal combustion engines and, more particularly, to a spark plug which provides a more efficient transfer of heat energy away from the ignition region of the spark plug.

The present invention is directed to a construction for a spark plug which allows it to operate more effectively than conventional spark plugs for long periods of time at a temperature high enough to prevent fouling, i.e., the formation of electrically conducting deposits on certaincomponents of the spark plug, but low enough to avoid ignition of a fuel-air mixture adjacent thereto before a spark occurs across the gap formed by the electrodes of the spark plug. Specifically, the

spark plug of this invention is formed in a manner such that it provides for the rapid transfer of heat from the spark plug itself to the engine block with which the spark plug is operably coupled. It also allows the major portion of the spark plug to be formed of insulating material of the type which is conventionally used for making the core members of spark plugs. Thus, the construction of the spark plug can be greatly simplified and its production cost can be significantly reduced while, at the same time, greater efficiency of spark plug operation can be realized because of the longer operating life of the spark plug made and used in accordance with the teachings of this invention.

The spark plug of this invention has a core member of insulating material, a central electrode within the core member, means for mounting the core member within a bore of an engine block so that one end of the first electrode projects into or communicates with a cylinder or combustion chamber associated with the engine block. and a second electrode having a mounting member which not only provides an electrical path between thesecond electrode and the engine block but also presents, because of its relatively high-thermal conductivity, a low impedance path for the efficient transfer of heat energy from the spark plug itself to the engine block adjacent thereto. The mounting member presents a relatively large surface area for engagement with the adjacent engine block by means of which heat is quickly transferred from the electrodes and the portions of the core member adjacent to the electrodes to the block for dissipation thereby in the usual manner. One form of the mounting member is a cuplike unit having an annular sidewall presenting the surface which is to engage the engine block and to which the second electrode is rigidly and electrically attached, This construction of the mounting member permits it to be easily attached to the core member, such as by a press fit, so that the core member and the mounting member form a unit which can be packaged and sold as a commercial product. Any suitable means can be provided for releasably mounting the core member in an operative position on the engine block. r

The spark plug of the present invention has a construction which permits it to operate in the temperature range of approximately 900 F. to 1300 F a range which is deemed preferable to prevent fouling and to avoid preignition. This feature is provided in the invention by positioning the electrode mounting member of high thermal conductivity on a tubular sleevelike portion which is in surrounding relationship to the nose portion of the core member. Thus, heat generated in the sleeve portion and the nose portion can rapidly dissipate to an engine block in which the spark plug is'disposed, through the mounting member. Thus, the mounting member not only serves to position the ground electrode adjacent to the central electrode but it also provides a relatively short path for heat developed in the end portions of the core member. The

mounting member presents a relatively large surface area engageable with both an engine block and the sleevelike portion on the spark plug to thereby provide a relatively high temperature gradient between the core member and the engine block. The construction of the spark plug also provides greater latitude in the design of the nose portion to assure that the spark plug, in normal operation, will have'a core temperature 1 in the nose portion of 900 F. to 1300 F.

In conventional spark plugs, the nose portion of the core member is surrounded by the threaded end of a metallic shell for connecting the spark plug to an engine block. The core member, being of a ceramic material, engages the shell along a relatively narrow, annular shoulder and this shoulder is substantially the only area at which heat conduction occurs from the nose portion to the engine block through the metal shell. Since the threaded part of the shell also is subject to the high temperatures in a combustion chamber, the shell itself rises in temperature sufficient to cause the above-mentioned shoulder to present a low temperature gradient for the heat developed in the nose portion. Thus, heat is very inefficiently transferred to the engine block from the nose portion and the temperature of the nose portion can rise to a value close to the preignition temperature, a level which is to be avoided for efficient engine operation. Moreover, the construction of conventional spark plugs requires that the nose portions be precisely dimensioned to provide the proper heating of the nose portion to avoid fouling. As a result, the conventional spark plugs are usually grouped ashot or cold plugs for use with cold and hot engines, respectively. l-lot plugs are operated at higher tip or nose portion temperatures than cold plugs for a given combustion chamber temperature. Thus, the plugs are generally limited to their uses in specific applications.

The present invention avoids these problems by providing a spark plug capable of efficiently operating over a wider range of combustion chamber temperatures than is capable with conventional spark plugs. Thus, the spark plug of this invention can be used with both hot and cold running engines. This end is achieved by the specific construction of the spark plug wherein the core and electrode mounting member are shaped to assure that the nonfouling temperature is quickly reached but that the preignition temperature is not attained for both high and low performance engines.

The primary object of this invention is to provide an improved spark plug which permits an efficient dissipation of heat energy from the spark plug body to an adjacent engine block in a manner such that the spark plug will operate in a temperature range to avoid fouling and preignition problems commonly associated with conventional spark plugs.

Another object of this invention is to provide a spark plug for an internal combustion engine wherein the spark plug has heat dissipation means of improved construction which permits heat to be conducted away from the spark plug to an 'en gine block along a relatively short path while allowing the major portion of the spark plug to be formed of insulating material to lower its cost and to simplify its construction.

Another object of this invention is to provide a spark plug and engine block combination wherein the spark plug is formed essentially of insulating material except for a relatively small portion which is formed of material having relatively high electrical and thermal conductivities to provide both an effective electrical path and a good heat transfer path to an engine block to provide for greater operating efficiency of the engine.

Other objects of this invention will become apparent as the following specification progresses, reference being had to the accompanying drawing for an illustration of an embodiment of the invention.

In the drawings:

FIG. 1 is a side elevational view, partly in section, of the spark plug of the present invention with the spark plug being mounted in an operative position in an engine block; and

FIG. 2 is an end elevational view of the spark plug looking in the direction of line 2-2 of FIG. 1.

The spark plug of this invention is broadly denoted by the numeral 10 and includes a main body or core 12 of a suitable insulating material, such as a ceramic having aluminum oxide as in ingredient. Body 12 has a number of axially spaced solid cylindrical portions, the first of which is cylindrical portion 14 integral with a second cylindrical portion 16 of a greater diameter than portion 14. The zone of body 12 between portions 14 and 16, denoted by the numeral 18, is beveled. A

third cylindrical portion 20 is between cylindrical portion 16 and a nose portion 22, the latter being surrounded by a tubular portion or sleeve 24, there being a beveled zone 26 surrounding the junction between cylindrical portion 20 and beveled zone 26. Portions 14, 16, 20, 22 and 24 are all integral with each other. The core is tubular to form a passage for a central metallic electrode which extends through body 12 and projects outwardly from opposed ends thereof. The central electrode has a tip 28 projecting outwardly from nose portion 22 and a terminal 30 projects outwardly from cylindrical portion 14, the terminal being adapted for electrical connection in a conventional manner to a distributor.

Spark plug is further provided with a cup-shaped metallic, electrode mounting member 34 which has a first annular sidewall portion 36 and a second annular sidewall portion 36, the latter having a greater outer diameter than sidewall portion 36 to present an annular shoulder 39 on member 34, there being an annular end wall 38 integral with sidewall 36 for underlying the end face of sleeve 24. End wall 38 could be constructed so that it extends partially across the entrance to the annular, axially extending space 40 between nose portion 22 and sleeve 24 so as to provide control of the volume of hot gases entering the space from a combustion chamber and thereby to provide some control of the temperature to which the nose portion and sleeve are elevated during engine operation using spark plug 10. The end of member 34 opposite to end wall 38 is open and the inner diameters of sidewall portions 36 and 37 is substantially equal to the outer diameter of cylindrical portion 22 of body 12. Member 34 is press fitted on cylindrical portion 22 so as to provide a snug fit thereon, whereby the outer surface of sleeve 24 is in substantial surface engagement with the inner surface of sidewall portions 36 and 37 to permit good contact and thereby optimum heat exchange relationship between sleeve 24 and mounting member 34. Nose portion 22 extends through the central opening in end wall 38 and tip 28 is spaced from end wall 28.

Mounting member 34 has an annular, beveled end face remote from end wall 38. This end face is shaped to conform to the configuration of beveled zone 26. A metallic sealing gasket 42 is disposed between the end face of sidewall 36 and zone 26 to prevent fluid flow past this junction and to permit a heat exchange between zone 26 and an engine block hereinafter described.

Member 34 is provided with an electrode 44 which is integral to end wall 38 by an arm 46. The arm is shaped to position electrode 44 in proximity to and spaced from tip 28 to present a spark gap 48 therebetween.

The spark plug is used with the block 49 of an internal combustion engine, the block having a bore 50 shaped to receive portions 16 and of body 12 and also to receive member 34. The outer surfaces of sidewall portion 37 is substantially coextensive with the outer surface of cylindrical portion 20. Thus, bore 50 will have a first cylindrical region for receiving cylindrical portion 16, a second cylindrical region of a reduced diameter for receiving cylindrical portion 20 and sidewall portion 37, and a third cylindrical region for receiving sidewall portion 36. The cylindrical inner surface portions of the engineblock defining the two regions of bore 50 are complemental to and are in surface engagement with substantially the entire portions of the outer surfaces of cylindrical portions 16 and 20 and with the outer cylindrical surface of sidewall portions 36 and 37 to thereby provide a relatively large surface area defining a conduction path for any heat energy absorbed in body 12 in the vicinity of nose portion 22 and cylindrical portions 16 and 20. The bore is open at both ends and is shaped to cause the spark plug to be positioned axially of the bore with spark gap 48 projecting slightly into a combustion chamber, one boundary of which is defined by end face 52 of engine block 49.

Bore 50 is shaped to present a shoulder 54 at the junction between the two adjacent cylindrical regions of the bore. This shoulder is beveled to conform to beveled annular zone 24 of body 12. A metallic-sealing gasket 56 is disposed between shoulder 54 and zone 24 and operates to facilitate the dissipation of heat energy to the engine block from body 12 in the same manner as gasket 42.

Bore 50 is countersunk and internally threaded at the end of the bore remote from member 34, whereby an externally threaded fastening element 58 can be used to releasably hold spark plug 10 in an operative position within bore 50. Element 58 has a first cylindrical part 60 receivable within the countersunk portion of bore 50 and a second polygonal part 62 integral with part 60 and having tool-engaging flats 64 thereon to facilitate the rotation of element 58 into a position holding the spark plug in bore 50. Cylindrical part 60 has a beveled inner face 66 which conforms to and overlies beveled zone 18 of body 12 to hold the spark plug in its operative position.

In use, spark plug 10 is inserted into bore 50 so that cylindrical portions 16 and 20 are properly seated in the bore and spark gap 48 is either in or in fluid communication with the combustion chamber whose one boundary is defined by end face 52. Member 34 will have been previously placed on body 12 about sleeve 24 either at the time the plug is made or at any time thereafter and before it is put into use. Member 34 is preferably press fitted onto portion 22 so that there will be interengagement between the entire abutting surfaces of these components to thereby provide a good heat exchange relationship therebetween. Shoulder 39 on member 34 forces a sealing gasket 62 against a corresponding annular shoulder on the engine block. Thus, member 34 will be retained in the bore and cannot drop off the core and into the combustion chamber. Fastening element 58 is then moved into place by rotating the same on body 12 so that it becomes threaded into the countersunk portion of bore 50. A suitable tool in engagement with flats- 64 will generally be needed to rotate element 58 until spark plug 10 is firmly seated in the bore. The spark plug can then be electrically connected to a distributor in the usual manner.

In its operative'position, spark plug 10 is mounted so that the outer surface of member 34 is in substantial contact with the inner surface of bore 50 directly adjacent thereto. This interengagement provides a good electrical contact between member 34 and engine block 49 and also gives rise to a good heat exchange relationship between member 34 and engine block 49. Thus, electrode 44 is electrically connected or grounded to the engine block while tip 28 is electrically connected through terminal 30 to the distributor. A voltage can, therefore, be developed across gap 48 to permit an arc to be periodically established for igniting a fuel-air mixture in the combustion chamber associated with the spark plug.

The construction of member 34 and its relationship to the engine block allows heat energy developed in member 34, due to the ignition of the fuel-air mixture, to be rapidly dissipated from member 34 to the engine block across the interface therebetween. Thus, member 34 is maintained at a relatively low operating temperature during operation of the engine although this temperature is above the fouling temperature of the spark plug and below the preignition temperature thereof. The temperature will, therefore, be in the range of 900 F. to 1300 F. Moreover, the heat developed or absorbed in body 12, specifically in portion 22, is rapidly dissipated through member 34 to engine block 49. This will prevent the tip 28 from substantially rising above the upper limit of the abovementioned temperature range. Thus, preignition is effectively restricted from occurring. On the other hand, the construction of the spark plug is such that the temperature is maintained on body 12 and the electrodes above 900 F. to minimize fouling of the spark plug. Any extraneous heat energy which is conducted to portion 20 is transferred directly to the engine block and gaskets 42 and 54 channel the heat energy in zones 26 and 24, respectively, to the engine block. Thus, the spark plug of this invention allows for rapid dissipation of heat energy from the ignition region so as to avoid the problems of fouling and preignition which oftentimes occur with the use of conventional spark plugs.

The spark plug of the present invention will operate properly at both relatively low and relatively high combustion temperatures and also at combustion temperatures between relatively low and high values. Thus, the plug has a wider.

"required minimum fouling temperature. During hot engine operation, there will be sufficient dissipation of the heat from nose portion 22 and sleeve 24 so that body 12 in the vicinity of the nose portion will remain relatively cool so as toresult in a relatively high temperature gradient between body 12 and member 34.

For purposes of illustration, spark plug has the following dimensions: the length of bodyl2 is approximately 64 mm.; the axial length of portions 16 and 32 is ll mm. and 2 mm., respectively; the angle of bevel of zones 18, 24 and 26 is approximately 30"; the diameter of the central electrode is 2.6 mm.; the diameter of portion 22 is 5 mm.; the diameter of portion 24 is 10 mm.; the diameter of portion is 14 mm.; and the diameter of portion 16 is l 8 mm.

lclaim:

l. A spark plug comprising: a core member of insulating material having a nose portion; a first electrode carried by said core member and having an end at one extremity of the nose portion; a second electrode; and means on the core member adjacent to said nose portion and having a relatively high thermal conductivity for electrically coupling the second electrode to an engine block and for mounting the second electrode on said core member in proximity to and spaced from the first electrode to define therewith a spark gap.

2. A spark plug comprising: a core member formed of insulating material and having a nose portion and a sleeve in surrounding, spaced relationship to said nose portion; a central electrode within the core member and having an exposed tip at said nose portion; an electrically and thermally conductive member carried by and disposed in surface engagement with the sleeve, said member being disposed to engage an engine block when the core member is disposed in an operative position in a bore of the engine block; and a second electrode carried by said member and disposed to present a spark gap with the first electrode.

3. A spark plug as set forth in claim 2, wherein said conductive member has a continuous sidewall, said sleeve being complementally received within the sidewall of said conductive member.

4. A spark plug as set forth in claim 3, wherein said sidewall is cylindrical, said core member having a cylindrical portion having an outer surface coaxial with said sidewall.

5. A spark plug as set forth in claim 2, wherein said conductive member is substantially cup-shaped to present a cylindrical sidewall and an end wall, the sidewall being in engagement with said one end of the core member, said end wall having a present an annular shoulder therebetween.

8. A spark plug comprising: an elongate body formed of an insulating material and having a nose: portion and a sleeve at one end thereof, the sleeve being in surrounding, spaced relationship to' said nose portion; a first electrode carried by and extending longitudinally of the'body and having an extremity projecting through and terminating at one end of said nose portion; an electrically conductive tubular member complemental to and in engagement with said sleeve and having an outer surface for engagement with an adjacent engine block when the body is inserted in and extends substantially through a bore in the en ine block, whereby said member provides a heat transfer pa between said cyi engine block; and a second electrode carried by said member and disposed to present a spark gap with said extremity of the first electrode.

9. A spark plug as set forth in claim LB, wherein said body has a cylindrical portion coaxial with said portion, there being an annular zone of juncture between said first and second cylindrical portions, said member having an annular end face adjacent to said zone, and wherein is included an annular gasket between said zone and said end face in sealing relationship thereto.

10. In combination: an engine block having a bore therethrough and a combustion'chamber adjacent to one end of the bore; an elongated core member of insulating material receivable within said bore, said core member having a nose portion and a sleeve in surrounding, spaced relationship to said nose portion; a first electrode extending through the core member and having a tip projecting outwardly from one end thereof; means engageable with the core member for releasably mounting the same in an operative position on the engine block with the core member extending through the bore and with said tip being in said combustion chamber; a second electrode; and electrically and thermally conductive means spanning the distance between and in surface engagement with said sleeve and the engine block for mounting the second electrode in a position to present a spark gap with said tip, whereby said mounting means provides an electrical path between said second electrode and said engine block and a heat transfer path between said one end of the core member and the engine block. l

11. The combination as set forth in claim 10, wherein said mounting means includes a cup-shaped member complemental to and in surface engagement with said nose portion and having a central opening, said tip extending through said opening and being spaced from said cup-shaped member.

12. The combination as set forth in claim 10, wherein said core member has a longitudinally extending portion adjacent to said nose portion and being complemental to and in surface engagement with the inner bore-defining surface of said engine block when said core member is in said operative position.

13. The combination as set forth in claim 10, said core member having first and second cylindrical portions complemental to and in surface engagement with the inner boredefining surface of said engine block when said core member, is in said operative position, said core member having a zone of juncture between said first and. second portions, said mounting means including a continuous sidewall having a first shoulder intermediate the ends thereof, said engine block having a second shoulder adjacent to said first shoulder, and wherein is provided sealing means for sealing the junction between said shoulders.

ndrical portion and said 

1. A spark plug comprising: a core member of insulating material having a nose portion; a first electrode carried by said core member and having an end at one extremity of the nose portion; a second electrode; and means on the core member adjacent to said nose portion and having a relatively high thermal conductivity for electrically coupling the second electrode to an engine block and for mounting the second electrode on said core member in proximity to and spaced from the first electrode to define therewith a spark gap.
 2. A spark plug comprising: a core member formed of insulating material and having a nose portion and a sleeve in surrounding, spaced relationship To said nose portion; a central electrode within the core member and having an exposed tip at said nose portion; an electrically and thermally conductive member carried by and disposed in surface engagement with the sleeve, said member being disposed to engage an engine block when the core member is disposed in an operative position in a bore of the engine block; and a second electrode carried by said member and disposed to present a spark gap with the first electrode.
 3. A spark plug as set forth in claim 2, wherein said conductive member has a continuous sidewall, said sleeve being complementally received within the sidewall of said conductive member.
 4. A spark plug as set forth in claim 3, wherein said sidewall is cylindrical, said core member having a cylindrical portion having an outer surface coaxial with said sidewall.
 5. A spark plug as set forth in claim 2, wherein said conductive member is substantially cup-shaped to present a cylindrical sidewall and an end wall, the sidewall being in engagement with said one end of the core member, said end wall having a central opening therethrough, said nose portion extending into the opening.
 6. A spark plug as set forth in claim 5, wherein the sidewall of said conductive member is press fitted on and in complementary surface engagement with said sleeve.
 7. A spark plug as set forth in claim 2, wherein said sidewall has a pair of cylindrical, coaxial portion, one portion having an outer diameter greater than that of the other portion to present an annular shoulder therebetween.
 8. A spark plug comprising: an elongate body formed of an insulating material and having a nose portion and a sleeve at one end thereof, the sleeve being in surrounding, spaced relationship to said nose portion; a first electrode carried by and extending longitudinally of the body and having an extremity projecting through and terminating at one end of said nose portion; an electrically conductive tubular member complemental to and in engagement with said sleeve and having an outer surface for engagement with an adjacent engine block when the body is inserted in and extends substantially through a bore in the engine block, whereby said member provides a heat transfer path between said cylindrical portion and said engine block; and a second electrode carried by said member and disposed to present a spark gap with said extremity of the first electrode.
 9. A spark plug as set forth in claim 8, wherein said body has a cylindrical portion coaxial with said portion, there being an annular zone of juncture between said first and second cylindrical portions, said member having an annular end face adjacent to said zone, and wherein is included an annular gasket between said zone and said end face in sealing relationship thereto.
 10. In combination: an engine block having a bore therethrough and a combustion chamber adjacent to one end of the bore; an elongated core member of insulating material receivable within said bore, said core member having a nose portion and a sleeve in surrounding, spaced relationship to said nose portion; a first electrode extending through the core member and having a tip projecting outwardly from one end thereof; means engageable with the core member for releasably mounting the same in an operative position on the engine block with the core member extending through the bore and with said tip being in said combustion chamber; a second electrode; and electrically and thermally conductive means spanning the distance between and in surface engagement with said sleeve and the engine block for mounting the second electrode in a position to present a spark gap with said tip, whereby said mounting means provides an electrical path between said second electrode and said engine block and a heat transfer path between said one end of the core member and the engine block.
 11. The combination as set forth in claim 10, wherein said mounting means includes a cup-shaped member complemental to and in surface enGagement with said nose portion and having a central opening, said tip extending through said opening and being spaced from said cup-shaped member.
 12. The combination as set forth in claim 10, wherein said core member has a longitudinally extending portion adjacent to said nose portion and being complemental to and in surface engagement with the inner bore-defining surface of said engine block when said core member is in said operative position.
 13. The combination as set forth in claim 10, said core member having first and second cylindrical portions complemental to and in surface engagement with the inner bore-defining surface of said engine block when said core member is in said operative position, said core member having a zone of juncture between said first and second portions, said mounting means including a continuous sidewall having a first shoulder intermediate the ends thereof, said engine block having a second shoulder adjacent to said first shoulder, and wherein is provided sealing means for sealing the junction between said shoulders. 